Tomáš Pavlíček, Davorka Hackenberger Kutuzović, Branimir Hackenberger Kutuzović Oren Pearlson, Jörn Theuerkauf, Christian Mille, Timea Szederjesi, Shweta Yadav, Csaba Csuzdi. How can we explain the current distribution of earthworms in Central Pacific?. In: Djerdj, T., Hackenberger Kutuzović, D., Hackenberger Kutuzović B. (Eds.) Book of Abstracts of the 10th International Oligochaeta Taxonomy Meeting (IOTM 2025), November 3–7, 2025, Osijek, Croatia. p. 49. ISBN 978-953-46841-0-8.
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| The New Caledonian biodiversity endemism in earthworms has been observed at the species
and genera phylogenetic levels. We organized three one-month expeditions (in 2014, 2023 and
2024) in New Caledonia for earthworm sampling. Traditionally, speciation on Grande Terre (the
main island of New Caledonia) was considered the result of long-term cladogenesis and tectoni-
cally largest volcanic events in the Earth history, including the break-up of Gondwana. However,
endemic earthworms in the tropical New Caledonia do not show the expected pattern of the trans-Pacific-(sub)tropical groups distributed between Australia, New Caledonia and the Americas. An example of the trans-Pacific (sub)tropical group is the land crocodile Mekosuchus inexpectatus that went extinct about 3000 years ago.
Five earthworm species – Acanthodrilus kermadecensis, A. mereensis, Pithemera sedgwicki, Metapheretima speiseri and Polypheretima fida – were described as endemic species of smaller islands (parts of five archipelagos) in the central Pacific. However, the fact that different islands belong to one of these archipelagos does not mean that they are of the same origin, the same age and that they have the same taxonomic composition. For instance, the northern Lau islands of the Fiji Archipelago are of volcanic origin, whereas the southern ones of the same archipelago are made of sedimentary carbonate or of uplifted coral reefs.
We concluded suggest that the trans-tropical Pacific distributions in animals might be related to the central Pacific tectonics which is responsible for the formation of large igneous plateaus and not to the Gondwana break up. The observed earthworm distributions might result from the emplacement of large igneous plateaus in the central Pacific during the Cretaceous, one of the largest volcanic events in the history of Earth. The mostly subaerial eruptions in the Ontong Java plateau and the Manihiki and Hikuragi plateaus indicate that distributions could be explained on an ad hoc basis by the extinction in other areas and not necessarily as the result of dispersal.
However, more work will be needed to explain the observed pattern in New Caledonian earthworms.
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